Application of swat model to assess the impact of land use changes on stream discharge in nghing tuong watershed thai nguyen province

THAI NGUYEN UNIVERSITY UNIVERSITY OF AGRICULTURE AND FORESTRY DINH NGOC HUAN TOPIC TITLE: “APPLICATION OF SWAT MODEL TO ASSESS THE IMPACT OF LAND-USE CHANGES ON STREAM DISCHARGE IN NGHINH TUONG WATERSHED, THAI NGUYEN PROVINCE” BACHELOR THESIS Study Mode: Full-time Major: Bachelor of Environmental Science and Management Faculty: International Training and Development Center Batch: 2010 - 2015 Thai Nguyen, January 2015 DOCUMENTATION PAGE WITH ABSTRACT Thai Nguyen University of Agriculture and Forestry Degree Program Bachelor of Environmental Science and Management Student name Dinh Ngoc Huan Student ID DTN1054110040 Thesis Tittle Application of SWAT model to assess the impact of land-use changes on stream discharge in Nghinh Tuong watershed, Thai Nguyen Province Suppervisor (s) Phan Dinh Binh, Ph.D Abstract: The purpose of this research is to implement “Soil and Water Assessment Tool (SWAT)” model and GIS to evaluation, assessment impact of land-use changes on stream discharge in Nghinh Tuong watershed (riverhead Cau river watershed) in Northern Viet Nam The watershed were cover by 56% forestry land, 30% agricultural land, and remain for others Stream discharge observed data 2002 2012 were used for calibration (2002 - 2007) and validation (2008 - 2012) The result shown that two coefficients (NSE and PBIAS) to evaluate model performance were 0.76 and 6.54% for calibration period and 0.87 and 4.74%, respectively Stream discharge strongly depends not only on quantity of precipitation but also on land use change Through the scenario 1, agricultural land (corn, orchard and tea) increases 9782.67 (2.45%), meanwhile forest (forest-mixed) decreases 1091.77 (2.75%) as compared to baseline scenario ii Additionally, precipitation increases 3.74% in mean wet season, but decreases 0.5% in mean dry season with respect to baseline period SWAT model was able to simulate stream discharge and sediment yield for Nghinh Tuong watershed successfully not only for Baseline scenario but also for Scenario In brief, SWAT proves its ability in simulation stream discharge and sediment yield in watershed level It is a useful tool to assist water quantity and quality management process in Nghinh Tuong watershed Keywords: Key words: stream discharge, watershed, GIS, SWAT model, scenario Number of pages: 50 Date of Submision : January 15, 2015 iii ACKNOWLEDGEMENT First and foremost, I wish to express my sincere thanks to the boards of Thai Nguyen University of Agriculture and Forestry, Dean of Faculty Natural Resources Management, Department of Remote sensing and Surveying of Thai Nguyen University of Agriculture and Forestry for providing me all the necessary facilities and all the teachers who built me the scientific knowledge to complete this research In particular, I would like to thank my principal research adviser Dr Phan Dinh Binh who guided me wholeheartedly when I implement this research project I place on record, my sincere gratitude to all staffs, government and people in Nghinh Tuong commune Vo Nhai district and Van Lang commune Dong Hy district, Thai Nguyen province for their expert, valuable guidance and generous support to our project Finally yet importantly, I take this opportunity to express our deepest appreciation to our families, relatives, friends and fellow students in class of K42-Advanced Education Program who encouraged and supported me unceasingly and all who, directly or indirectly, have lent their helping hand in this venture Thank you very much! Thai Nguyen, January 15, 2015 Student Dinh Ngoc Huan iv TABLE OF CONTENTS ACKNOWLEDGEMENT iv TABLE OF CONTENTS v LIST OF TABLES viii LIST OF FIGURES ix LIST OF ABBREVIATIONS xi Part 1: INTRODUCTION 1.1 Research rationale 1.2 Research’s objectives 1.3 Research questions and hypotheses 1.4 Limitations 1.5 Definitions Part 2: LITERATURE REVIEW 2.1 Research situation 2.2 Soil and Water Assessment Tool (SWAT) Model 2.2.1 Concept of SWAT 2.3 SWAT Theory 2.3.1 SWAT hydrologic component 2.3.2 The land phase of the hydrologic cycle 2.3.2.1 Climate 2.3.2.2 Hydrology 2.3.3 Routing phase of the hydrologic cycle 10 2.3.3.1 Routing in river 10 v 2.3.3.2 Routing through reservoirs 10 2.3.3.3 Sediment routing 10 2.4 Component processes in model (Neitsch et al., 2005a) 11 2.4.1 Surface runoff 11 2.4.2 Underground Flow 13 2.4.2.1 Lateral subsurface flow 13 2.4.2.2 Underground flow 13 2.5 SWAT sediment component (Neitsch et al., 2005a) 14 2.5.1 The Modified Universal Soil Loss Equation (MUSLE) 14 Part 3: METHODS 16 3.1 Materials 16 3.1.1 Description and topography 16 3.1.2 Climatic characteristics 18 3.2 Methods 19 3.2.1 Watershed delineation 19 3.2.2 Soil classification and soil physical characteristics 19 3.2.3 Land cover classification 20 3.3 SWAT model 20 3.4 SWAT model performance evaluation 22 Part 4: RESULTS 25 4.1 Overview of Nghinh Tuong basin 25 4.2 Preparation input data 26 4.2.1 Climatic parameters 26 4.2.1.1 Precipitation 29 vi Additionally, precipitation increases 3.74% in mean wet season, but decreases 0.5% in mean dry season with respect to baseline period SWAT model was able to simulate stream discharge and sediment yield for Nghinh Tuong watershed successfully not only for Baseline scenario but also for Scenario In brief, SWAT proves its ability in simulation stream discharge and sediment yield in watershed level It is a useful tool to assist water quantity and quality management process in Nghinh Tuong watershed Keywords: Key words: stream discharge, watershed, GIS, SWAT model, scenario Number of pages: 50 Date of Submision : January 15, 2015 iii LIST OF TABLES Table 4.1 Summarized climatic characteristics (1983- 2012) of Nghinh Tuong watershed for SWAT simulation 27 Table 4.2 Total monthly precipitation in Nghinh Tuong watershed from 1983 to 2012.(mm) 30 Table 4.3 Observed monthly stream discharge at Nghinh Tuong outlet from 2002 - 2012 (m3/s) 32 Table 4.4 Sub-watershed characteristics of Nghinh Tuong watershed 35 Table 4.5 Sub-outlet’s characteristics of Nghinh Tuong watershed 36 Table 4.6 Land use scenarios for Nghinh Tuong watershed 39 Table 4.7 Observed and simulated stream discharge for each period in Nghinh Tuong watershed 42 Table 4.8 Coefficients of monthly NSE and PBIAS as calibrating and validating stream discharge 44 Table 4.9 Stream discharge of Scenarios (2020) and Baseline scenario in Nghinh Tuong watershed (m3/s) 46 Table 4.10 Stream discharge of Scenarios (2030) and Baseline scenario in Nghinh Tuong watershed (m3/s) 47 viii LIST OF FIGURES Figure 3.1: Map of Vo Nhai District 18 Figure 3.2 SWAT soil database builder schematization 20 Figure 3.3 Application of SWAT on Nghinh Tuong watershed for simulation stream discharge and sediment load 22 Figure 4.1: The position of Nghinh Tuong basin 25 Figure 4.2 Monthly maximum, minimum and average temperature in Nghinh Tuong watershed from 1983 to 2012 28 Figure 4.3 Monthly relative humidity in Nghinh Tuong watershed from 1983 to 2012 28 Figure 4.4 Monthly wind speed in Nghinh Tuong watershed from 1983 to 2012 29 Figure 4.5 Total monthly precipitation in Nghinh Tuong watershed from 1983 to 2012 31 Figure 4.6 Observed monthly stream discharge at Nghinh Tuong outlet from 2002 - 2012 32 Figure 4.7 Digital elevation model (DEM) and stream network of Nghinh Tuong watershed 33 Figure 4.8 Map of land use status Nghinh Tuong River basin in 2012 34 Figure 4.9 Soil map of Nghinh Tuong River basin in 2012 34 Figure 4.10 Sub-watershed and stream network of Nghinh Tuong watershed 35 Figure 4.11 Map of Baseline Land use scenario (2012) for Nghinh Tuong watershed 40 Figure 4.12 Map of Land use scenario 1(2020) for Nghinh Tuong watershed 40 ix Figure 4.13 Map of Land use scenario (2030) for Nghinh Tuong watershed 41 Figure 4.14 Observed versus simulated monthly stream discharge and precipitation of Nghinh Tuong watershed during calibration and validation periods 43 Figure 4.15 Observed versus simulated average monthly stream discharge during calibration and validation periods of Nghinh Tuong watershed 44 Figure 4.16 Locations of land use change for scenario (2020) for Nghinh Tuong watershed 45 Figure 4.17 Locations of land use change for scenario (2030) for Nghinh Tuong watershed 47 x Figure 4.11 Map of Baseline Land use scenario (2012) for Nghinh Tuong watershed Figure 4.12 Map of Land use scenario 1(2020) for Nghinh Tuong watershed 40 Figure 4.13 Map of Land use scenario (2030) for Nghinh Tuong watershed 4.4 Assessing the impact of land-use changes on stream discharge in Nghinh Tuong watershed, Thai Nguyen Province 4.4.1 Baseline scenario The daily observed and simulated stream discharge were calculated and summarized into mean wet season, mean dry season, and mean annual Results from Table (4.7) indicate that the simulated data is lower than observed data for both mean wet and dry season for calibration (2002-2012) For example, mean wet and dry season of observed data were 24.85 and 5.13 (m3/s), while for simulated data were 14.42 and 24.15 (m3/s), respectively 41 Table 4.7 Observed and simulated stream discharge for each period in Nghinh Tuong watershed Calibration Validation Entire Period (2002-2007) (2008-2012) (2002-2012) Items Observed (m3/s) Mean annual Mean wet season Mean dry season 15 10.90 12.95 24.85 18.55 21.70 5.13 3.35 4.23 Simulated (m3/s) Mean annual 14.42 10.71 12.55 Mean wet season 24.15 18.35 21.24 Mean dry season 4.65 3.10 3.90 42 PART I INTRODUCTION 1.1 Research rationale Nghinh Tuong is the upland stream of Cau river in which supplies water for domestic, agriculture and industrial sectors in Thai Nguyen It is a vital resource for any human activities and living However, the river basin has been affected seriously by the economic growth caused the pollution and depletion clean water resources, and extremely climate events as drought and flooding If we not have appreciated solution for protecting the resources, we have to pay an expensive cost in the near future On the other hand, the intensive agriculture, overexploitation heavy metals as well as deforestation have lately been raising many problems in this basin The farmers cultivate agricultural crops, (especially in slope land) and overuse of pesticides and fertilizers for crops, which makes not only soil erosion but also pollutants load on stream into downstream Nevertheless, there have been no comprehensive assessments of land use change impact in this river basin Hence, a modeling effort to simulate these problems in Nghinh Tuong watershed should be implemented Under these circumstances, we proposed the research project “Application of SWAT model to assess the impact of land-use changes on stream discharge in Nghinh Tuong watershed, Thai Nguyen Province” 1.2 Research’s objectives The rapid economic growth has affirmed that Thai Nguyen is a major social and economic center of the Northern midland and mountainous area of Vietnam On the flip side however, the environment has suffered the degradation, exposed the population to serious air and water pollution, including watershed Table 4.8 Coefficients of monthly NSE and PBIAS as calibrating and validating stream discharge Simulation period Period Monthly NSE PBIAS (%) Calibration 2002 - 2007 0.76 6.54 Validation 2007 - 2012 0.87 4.74 Table 4.8 shows the results of the evaluation model through the NSE index PBIAS index quite good + Commissioning phase (2002-2007) NSE index = 0.76; PBIAS = 6.54 + Testing phase (2008-2012) NSE index = 0.87; PBIAS = 4.74 Figure 4.15 Observed versus simulated average monthly stream discharge during calibration and validation periods of Nghinh Tuong watershed 44 Figure 4.15 illustrates that SWAT tends to underestimate stream discharge for major months of year The conceivable reason contributing to this result is the land use map generated based on year 2010 survey data which may cause differences in land use installed in the previous period Another reason causing discrepancy between simulated and observed sediment yield may be attributed to soil types 4.4.2 Land use scenario (2020) Stream discharge of Scenario results at Nghinh Tuong outlet were summarized in Tables 4.9, and Figure 4.16 Figure 4.16 Locations of land use change for scenario (2020) for Nghinh Tuong watershed 45 Table 4.9 Stream discharge of Scenarios (2020) and Baseline scenario in Nghinh Tuong watershed (m3/s) Stream discharge (m3/s) Precipitation (mm) Items Mean annual Baseline Scenario Baseline Scenario Difference Change Scenario Scenario (%) 1698.0 1753.12 14.42 14.93 0.50 3.46 1390.2 1453.78 24.15 25.20 1.05 4.35 305.8 297.34 4.65 4.60 -0.05 -1.09 Mean wet season Mean dry season In general, stream discharge strongly depends not only on quantity of precipitation but also on land use change; high precipitation will lead to high stream discharge and land use change with increasing agricultural land will reduce stream discharge, especially in dry season In Mean wet season, precipitation increases 63.58 mm (4.57%) from 1390.20 mm in 2012 to 1453.78 mm in 2020 In this case, stream discharge in 2020 is 25.20 m3/s, increases 1.05 m3/s (4.35%) in comparison with baseline scenario period However, in Mean dry season, stream discharge in 2020 decreases 0.05 m3/s (1.09%) in comparison with baseline scenario period, from 4.65 m3/s (2010) to 4.60 m3/s (2020) Meanwhile, precipitation decreases 8.46 mm (2.77%) from 305.80 mm in 2010 to 297.34 mm in 2020 Therefore, mean annual of stream discharge just increases 3.46% (from 14.42 m3/s to 14.93m3 /s) with respect to baseline period 46 4.4.3 Land use scenario (2030) Figure 4.17 Locations of land use change for scenario (2030) for Nghinh Tuong watershed Table 4.10 Stream discharge of Scenarios (2030) and Baseline scenario in Nghinh Tuong watershed (m3/s) Precipitation (mm) Items Mean annual Stream discharge (m3/s) Baseline Scenario Baseline Scenario Difference Change Scenario Scenario (%) 1698.0 1771.58 14.42 15.05 0.63 4.37 1390.2 1478.26 24.15 25.48 1.33 5.51 305.8 291.32 4.65 4.56 -0.09 -1.94 Mean wet season Mean dry season 47 degradation The cause of the watershed degradation is mainly due to overexploitation of natural resources and land use change Nghinh Tuong watershed located in Vo Nhai district, Thai Nguyen province is a sub-basin of Cau river basin, which is the biggest river basin in Viet Nam Its estimated length is 46 km, and it drains an area of 397 km2, discharging thousands of irrigation demand annually for people in Nghinh Tuong commune (NTPC, 2010) Approximately 40% of the river's length travels the limestone walls, valleys and steep cliffs, especially, passes through Than Sa protected areas which has been containing diverse of rare plant and animal species Since the economic renewal campaign (Doi Moi), most of areas in the river basin have been converted to other farming land types and levels, which bring more economic benefits On the other hand, deforestation and intensive agricultural land practices put a high pressure on land In addition, recently the illegal extraction of sand, gravel, gold and forest production have impacted broadly on environment, water quantity and quality which leads to soil erosion, degradation, sediment and nutrient deposition in this river basin The recent studies showed that water discharge depends not only on the precipitation, but also on land use types Gassman et al, (2007) stated that water discharge based on proportion of arable land and forested land in the basin Once the water discharge increases, it leads to the step-up of soil erosion rate, reduction of soil fertility and downstream flooding during the rainy season Furthermore, the soil loss can transport pollutants in land as pesticides, heavy metals, waste to downstream basin causing seriously impact on the living environment of aquatic species and human health (Ella, 2005), especially in dry season PART CONCLUSIONS AND DISCUSSION 5.1 Conclusions In this research, SWAT model was setup, calibrated and validated successfully at Nghinh Tuong watershed with the drainage area of 39700.58 In order to assess the impacts of land use change on stream discharge and sediment yield in Nghinh Tuong watershed, the land use scenarios were formulated combined with climate change in SWAT simulation In scenario 1, agricultural land (corn, orchard and tea) increases 786.08 (1.98%), meanwhile forest (forest-mixed) decreases 1091.77 (2.75%) as compared to baseline scenario Additionally, precipitation increases 3.74% in mean wet season, but decreases 0.5% in mean dry season with respect to baseline period In scenarios 2, agricultural land increases 1348.87 (3.39%) meanwhile forest decreases 1838.14 (21.41%) with respect to baseline scenario respectively Furthermore, precipitation increases 6.33% in mean wet season, but decreases 4.74% in mean dry season for scenario SWAT was able to simulate stream discharge and sediment yield for Nghinh Tuong watershed successfully not only for Baseline scenario but also for Scenario During calibration process, sensitive parameters were identified as: CN2 (curve number), ESCO (soil evaporation compensation factor), EPCO (plant uptake compensation factor), C FACTOR (cover and management factor) Simulation result for Baseline scenario showed a good agreement between observed and simulated data SWAT shows its high capability in stream discharge Through this research we have constructed Actiview database and Spatial databases for SWAT model 49 The results of running the model calculated stream discharge for the period (2002 - 2012) shows that Mean annual: 12,55 m3/s Mean wet season: 21.24 m3/s Mean dry season: 3.90 m3/s The results of the evaluation model through the NSE index PBIAS index quite good In brief, SWAT proves its ability in simulation stream discharge and sediment yield in watershed level It is a useful tool to assist water quantity and quality management process in Nghinh Tuong watershed 5.2 Discussion The Application of SWAT model is very large However, the input data requirements for models and need much time to process the data especially, maps like topographic maps, soil maps, forest maps and their attribute data To be able to use this model to quantitatively assess the impact of the floods forest necessarily have a uniform data input So that, the following time, we need to investigate basic data such as meteorology, climate, land, soil, hydrology, forest etc to be able to put the model into more widespread use The model was validated for stream discharge and sediment yield at main outlet, but not yet validated for sub-outlets due to the limited data Hence, the validation process for stream discharge and sediment yield process at some important sub-outlets must be done in the next step to ensure the validity of simulation In Nghinh Tuong watershed, when farmers cultivate agricultural crops, (especially in slope land) and apply pesticides and fertilizers for crops, which 50 make not only soil erosion but also pesticides and phosphorous load on stream into downstream However, there were no comprehensive assessments of pesticides loads in this river basin Hence, a modeling effort to simulate these problems in Nghinh Tuong watershed should be implemented in the near future 51 REFERENCES Arnold, J G., J R Williams, and D R Maidment 1995 Continuous-time water and sediment-routing model for large basins Journal of Hydrology Engineering, ASCE 121(2): 171-183 Arnold, J G., R S Muttiah, R Srinivasan, and P M Allen 2000 Regional estimation of base flow and groundwater recharge in the upper Mississippi basin Journal of Hydrology 227(1-4): 21-40 Arnold, J G., R Srinivasan, T S Ramanarayanan, and M Di Luzio 1999 Water resources of the Texas gulf basin Water Science and Technology 39(3): 121-133 Ella, V B 2005 Simulating soil erosion and sediment yield in small upland watersheds using the WEPP model In: I Coxhead and G.E Shively, Land use change in tropical watersheds: Evidence, causes and remedies CABI publishing Wallingford, Oxfordshire, UK, p109-125 Gassman, P.W., M.R Reyes, C.H Green, and J.G Arnold The Soil and Water Assessment Tool: historical development, applications, and future research directions Transaction of ASABE 50(4): 1211-1250 Govender, M., and C S Everson 2005 Modelling streamflow from two small South African experimental catchments using the SWAT model Hydrology Processes 19(3): 683-692 GSOV (General Statistics Office of Viet Nam) 2008 Statistical year book 2008, National Political Publishing House, Ha Noi, Viet Nam Moriasi, D N., J G Arnold, M W Van Liew, R L Binger, R D Harmel, and T Veith 2007 Model evaluation guidelines for systematic quantification of accuracy in watershed simulations Transaction of ASABE 50(3): 885-900 Nash, J E., and J V Sutcliffe 1970 River flow forecasting through conceptual models: Part I A discussion of principles Journal of Hydrology 10(3): 282290 Neitsch, S L., J G Arnold, J R Kiniry, and J R Williams 2005a Soil and Water Assessment Tool Theoretical Documentation, Version 2005 Temple, 52 This study are (1) to apply (SWAT) model in a small watershed in Thai Nguyen to assess the long-term impact of land-use changes on stream discharge; (2) to understand the behavior of the river based on land use types; and (3) to provide appropriate suggestions to sustain the soil and water resources 1.3 Research questions and hypotheses How the intensive agriculture, overexploitation heavy metals as well as deforestation have lately been raising many problems in Nghinh Tuong basin ? What is the modeling effort to simulate these problems in Nghinh Tuong watershed? The application of SWAT model-Soil and Water Assessment Tools understand the effect of land-use changes on stream discharge and prove its ability in simulation stream discharge in watershed level and then provide appropriate suggestions to sustain the soil and water resources 1.4 Limitations The Application of SWAT model is very large However, the input data requirements for models and need much time to process the data, the input data requirements for models and need much time to process the data To be able to use this model to quantitatively assess the impact of the floods forest necessarily have a uniform data input the model was validated for stream discharge and sediment yield at main outlet, but not yet validated for sub-outlets due to the limited data 1.5 Definitions Nowadays, the land use changes impact assessment on stream discharge in Nghinh Tuong watershed using SWAT model and GIS techniques has been Van, L., M W., and J Garbrecht 2003 Hydrologic simulation of the Little Washita River experimental watershed using SWAT Journal of American Water Resources Association 39(2): 413-426 Williams, J R 1975 Sediment routing for agricultural watersheds Water Resources 11(5): 965-974 54 ... Tittle Application of SWAT model to assess the impact of land- use changes on stream discharge in Nghinh Tuong watershed, Thai Nguyen Province Suppervisor (s) Phan Dinh Binh, Ph.D Abstract: The purpose... in Nghinh Tuong basin ? What is the modeling effort to simulate these problems in Nghinh Tuong watershed? The application of SWAT model- Soil and Water Assessment Tools understand the effect of. .. a small watershed in Thai Nguyen to assess the long-term impact of land- use changes on stream discharge; (2) to understand the behavior of the river based on land use types; and (3) to provide